1. Technical Field
The field of the present invention is transporting sheets in an office machine. More specifically, the invention relates to a shunt for reversing the conveyance direction of a document or the like.
2. Background Art
With office machines such as printers, copiers and the like, it is frequently desirable to reverse the conveyance direction of a document. The document is, for example, a paper sheet or the like provided with recordings. Reversing the document needs to be accomplished such that the document is transported first with its front edge leading, and is then further conveyed with its rear edge leading.
Others have addressed reversing the conveyance of a sheet of paper. For example, it is known from DE 32 17 115 A1 to accept the leading edge of an arriving document with a reversible roller pair whose direction of rotation can be reversed. In front of the reversible roller pair is disposed a pivotable guidance roller. When the document has been pulled in by the reversible roller pair such that the document's rear edge has reached the guidance roller, the direction of rotation of the reversible roller pair is reversed and the guidance roller is pivoted such that the document is steered by the guidance roller into the desired direction for further conveyance with the document's rear edge leading. This known shunt has the disadvantage that a succeeding next document can only be supplied to the reversing roller pair when the preceding document has been completely output by the reversing roller pair. Consequently the shunt hinders the conveyance of the documents and limits the continuity of document conveyance.
In another known example, DE 195 06 181 A1 shows a shunt where a sheet is supplied by front-end rollers to a reversible roller pair whose direction of rotation is reversible. The reversible roller pair accepts the sheet supplied by the front-end rollers and conveys it until the rear edge of the sheet is released by the front-end rollers and has been pulled over a wedge-form shunt element. The direction of rotation of the reversing roller pair is subsequently reversed such that the rear edge of the document is now leading and is transported past the shunt element to the output rollers. As soon as the output rollers have taken hold of the sheet and are conveying it in the output direction, the reversing roller pair is opened such that the next succeeding sheet can be guided by the front-end rollers into the open gap of the reversing roller pair. It is thereby possible to guide the particular succeeding next sheet into the reversing roller pair before the preceding sheet is completely pulled out of the reversing roller pair. The front-end roller and the output roller cooperates with a common pressure roller such that the drawing-in speed of the front-end roller and the output speed of the output rollers are, by necessity, equal. The output speed thereby limits the drawing-in speed of the front-end roller.
Thus, there exists a need for a shunt which makes possible a closer continuity sequence of the conveyed documents.